1. Field of the Invention
This invention relates to a tool for servicing subterranean gate valves employed in underground utility pipelines. It differs from known valve maintenance tools in that it is designed to remove and replace the operating nut used on certain types of gate values instead of the conventional wheel handle and is characterized mainly by its simplicity, cost effectiveness and reliability.
2. Description of the Prior Art
U.S. Pat. No. 4,573,378 to McDonald discloses a hand tool for removing the wheel handle from a subterranean gate valve. The tool comprises an elongated wrench member including a shaft of sufficient length to reach down through the valve tile to the gate valve at the bottom. The shaft has a handle at its upper end for rotating the shaft and a socket at its lower end adapted to engage the securing nut which holds the wheel handle to the valve stem. A tubular member having an impact surface is movably mounted over the shaft and includes at its lower end a pair of spaced apart vertical arms with offset segments at their ends. The offset segments engage and retain the wheel handle while the shaft is rotated to loosen the securing nut and permit removal of the handle. To assist in such removal, the tubular member is equipped with a slide which can be used as a hammer against the impact surface to provide a vertical force sufficient to loosen the wheel handle if necessary.
U.S. Pat. No. 4,601,077 to Doty discloses a tool for removing dirt and debris from inside the valve tile and for gaining access to a gate valve located at the bottom of the tile. The gate valve is of a different type than that disclosed in the McDonald patent, supra, in that the valve is controlled by a square operating nut placed over the top of the valve stem. The tool includes a handle attached to the upper end of an elongated shaft and a cylindrical part removably affixed to the lower end of the shaft. The cylindrical part has a bore which fits over the operating nut and a helix or auger which surrounds its outer surface. The helix or auger collects and removes the dirt and debris from the valve tile when the handle is rotated. Once the valve tile is cleared, the tool is removed and the cylindrical part is replaced by a square socket which can then be used in a conventional way for turning the operating nut to open and close the gate valve.
The problem with subterranean gate valves of this latter type is that the operating nut, which is usually made of cast iron, corrodes readily over time and looses its shape, that is, the nut becomes more round or less square, so that the nut is no longer useful for turning the square valve stem for operating the valve. In such instances, it may become necessary to excavate the earth around the valve tile to expose the valve and replace the valve operating nut. This can be a time-consuming and costly procedure.